Rubber-deterioration retarber and process of making



Patented May 3, I

- U I- E STAT SPAT TOF CE SIDNEY M. CADWELL, or Lnoma, new JERSEY, AssIeNoR TO THE TYNAUGATUGKY CHEMICAL commits, A oozar'oim'rron or CONNECTICUT. 1

deterioration No Ilrawin g.

RUBBER-DETERIQBATION nn'rirnnnn m) rnoonss or AKING.

This invention relates? to a rubber deterioration retarder and the process of making same, more particularly to the deterioration retarder formed by the condensation of acetaldehyde and aromatic amines in" acid solutiom'and the process of making same.

, Aserious difficulty in use of rubber articles is themore or less rapid deterioration of such articles depending on various condi. tions such as the stock employed, the fornii ot the article, the conditions under which it is used andother variables.

1923 there is described a process for over coming deterioration of rubber, balata and qutta percha caused by oxidation, and among the substances disclosedfor overcoming such is the acetaldehyde-aniline Y condensation product prepared in acid solution. The present invention relatesto this and similar deterioration preventing materials an d the method of making the same.

An object of my invention is to provide a simple, rapid and'easily carried out process.

for. producing an aldehyde-amine acid condensate; Another object is tolprovide' a process for substantially completely combining equi-molecular proportions of acet-' aldehyde and an aromatic amine in acid solution. -Anotherobject is toprovide a process for making an acid condensate of 1 the character described which'will substantially eliminate waste products'and which may be continuously carried out. Another ob ect is to provide alretarder o't deteriora lion in rubber which lsstable, substantially in the torm'of latex, in its plastictormion" the mill, or by treating" the rubber witlrthe I retarding material insolution. Other; ob-

' iects will appear ,from .the

detailed disclosure inthe specification. I

Theinventlon consists broadly in the pre- "terred form, in combining equi-molecular proportions ot acetaldehyde and 'anaromatic amine in acid solution,precipitatlngthe desired 'acetaldehyde-aromatic amine-acid cone The principal causes ofthis deterioration are overvulcanl- In my copending. applications Sn Application filed September 23, 1924. Serial No. 739,348

densate by v t he additionot a base, and re moving, and Washing Fthe precipitate. It

also comprises a eontinuouspro'cess by which the acid filtrateseparated from the precipi- ,tate: at the end oi each operation is again reacted upon to produce successive precipi tates or the desired material without substant al loss of by-produ'cts. The invention also comprises the products of the process.

This application is a continuation in part of application Serial--No. 641,764, filedMay 2c, 1923. x p

The preferred method "will first be described by which the substantially complete combination of equi-molecular amounts of acetaldehyde and an aromatic amine such as aniline can be secured, with a resulting con densation product which-is a very efiicient retarder of deterioration and substantially does not accelerate vulcanization. The products obtained by the 'use'of other pro.- portions are also retarde rs of deterioration. To prepare such a product .93 grains-of aniline may be dissolved in .500 00s. of twice normal hydrochloric acid, the solution cooled and to the stirred aqueous solution of the aniline hydrocloride there is then added a'4050 s0luti'onof44 grams of acetaldehyde made up in normalacid or water, the latter solution being added at such a speed that the temperature does not rise above 25 C. In-order to preventsuch rise in temperature it may benece'ssary to add some ice. After the acetaldehyde has all been added, thefsolutionis stirred f0r 30 min. Between .Sandqilof the acid is then neutralized with sodium; hydroxide,resulting. in the precipitation ot'the desired acetaldehyde-aniline acid condensate as a free 7 base in a powdered form which can be easily filtered. 1 It isdesirable that the acid be not completely neutralized as otherwise anyunhyde-aniline condensateto form a gum in Stead of a powder. The precipitate is then sepz'irated'by filtration and dried.

.The acid" condensate thus obtained is in the form :of a yellow amorphous powder having a melting point below C. and 7 above 50 C. It is completely soluble in aniline and mixturesof alcohol and benzol, but only partially soluble in alcohol, benzol, or ether alone; It should be completely soluble in a mixture of 41 parts of. benzol and 1 part of alcohol, and should dissolve in l- .normal hydrochloric acid to yield a clear reddish solution. It dissolves in mineral acidto yield a dark reddish brown solution. It is uite stabie under ordinary conditions and may be kept for extended periods of time without deterioration. On standing exposed to air for several days the outer surface undergoes a deepening in color, but this change ap: :iientl.y does not impair its qualities.

In order to render the process continuous and avoid by-products, the procedure in the above example may be slightly modified by adding a second equi-molecular proportion oi analine, that is about 03 grams, to the reaction product oi the acetaldehyde and aniline instead of sodium hydroxide. The aniline being a stronger base than the condensation product precipitates the latter, leaving in solution substantially 93 grams of aniline in the hydrochloric acid. After filtering oli and washing the acctali'lehyde-aniline condensate. the liltrate containing aniiine hydrochloride and some condensate has added thereto a suiiicient amount of wash water to again make 500 ccs. of solution as originally started with, and this solution again reacted upon with acetaldehyde. The acidity should be maintained between onehalf and twice normal, and this may be accomplished by adding 8 to 10 cos. of 13 normal hydrochloric acid to each succeeding preparation.

By the processes above outlined an almost complete combination or" equi-molecular proportions of acetaldehyde and aniline is obtained, the yield being about 95%. Vv hile in the examples 'iven hydrochloric acid has been employed as the preferred substance it is possible to also use another strong acid such as sulphuric acid. However, hydro chloric acid is stronger and accelerates the condensation more than sulphuric acid. Another objection to the use of sulphuric acid is that aniline hydrochloride is very soiuble while aniline sulphate is quite insoluble, and the amount of sulphuric acid requircd is about 5 times by volume the quantity needed when hydrochloric acid is used. and the maximum yield with sulphuric acid has been about 70%.

As another example of the process for obtaining the acetaldehyde-aniline acid condensate, the follwing is given, which is the process set forth in my co-pending application No. 656,453, before mentioned. A molecular weight of aniline dissolved in a molecular weight of approximately normal by drocbloric acid is treated with 1 molecular weights of acetaldehyde in approximately 50% aqueous solution. It will be observed that the hydrogen ion concentration of the reaction mixture is greater than 1X10? A reaction occurs as indicated by the heat evolved. About 30 min. after the two solutions have been mixed about nine-tenths of the acid is neutralized with normal soduim hydroxide which is added slowly with con tinuous stirring. This operation precipitates a light colored solid which is separated by liltration and washed substantially tree of chlorides with water. After drying the material is ready for use.

The material is a light colored solid which softens at 85 (3., or below, and is completely melted below 150 C. On melting it is converted into a reddish liquid. Its color changes slightly on exposure to air. It is insoluble in water, soluble in hydrochloric acid, only slightly soluble in ligroin and completely soluble in a mixture of benzol and ethyl alcohol. This material retards deterioration of rubber but does not appreciably accelerate the vulcanization or rubber.

The material is believed to consist of several acetaldehyde-aniline condensates including the two isomers of (ii-molecular ethylideneaniline melting at 85 C. and 126 C. (Ber. d. deut. Chem. Ges. 25, 2020; L7, 1296). These isomers have been isolated and found to retard the deterioration of rubher and not to accelerate the vulcanization of rubber.

The condensation of acetaldehyde and aniline has also been carried out under varying conditions as follows:

One mole of acetaldehyde and two moles of aniline were condensed in the presence of a small amount of alkali or in a chilled aqueous solution and yielded a white crystalline solid having a melting point of 51 C. This product was unstable at ordinary temperatures and decomposed somewhat while being milled into rubber. 1t retarded deterioration but also accelerated vulcanization.

Two moles of acetaldehyde and one mole of aniline were condensed in a concentrated acid solution and the reaction minture allowed to stand for a long time. The solution was then made alkaline and an ocher yellow amorphous compound was precipi tated, which hada melting point of l70180 C. This is the so-called Schultz base (Ber. d. deut. Chem. Ges. 207i) and possesses neither. retarding nor accelerating qualities. It the condensation is carried out in a weakly acid or basic solution the product formed isthat disclosed in may Patent No. 1,-i17,970, May 30, 1922, which is an excellent accelerator o't vulcanization and also a retarder of deterioration.

By the direct addition oi one mole of acetaldehyde to one mole of chilled aniline. water'and a yellow oil were formed. The oil became red on standing and is an eccelerator as well as aretard er of deterioration. If the condensation is carried out in alcoholic solution at a temperature oi' 0 C. di-

: molecular ethylidenel aniline is formed asa white crystalline solid having a melting polnt of 126 C. ThlS compound 1s an excellentretarder of deterioration and 13110 an accelerator of vulcanization. t I As showing that the,acetaldehyde anihne acid condensation product is not an accelerator of vulcanization, the following test was made: 100 parts of pale crepe, parts zinc oxide, 3 parts sulphur, and 1 part acid condensate were compormdcd in the usual manner and heated in a mold for 60 minutes under 4:() lbs. steam pressure. The resulting breaking.

' over the previously used stocks.

product showedvery poor vulcanization and had atensilestreng th of less than 1800' lbs. per sq; in. The acid condensate is also valuable by reasonof its adaptability under various conditions,since it may be used either with vulcanized ornnvulcanized rubber,ba-

lata, or gutta p'ercha, and it used in the unvulca'nized material the property of retarding deterioration persist-s after vulcanization. It may be milled into rubber, mixed directly with'latex, or applied to the maferial in the form of a. solution. In general from 3- 5% of the condensate with 100 parts of rubber retards the oxidation aging of any stock from 1004 OO%. This retarding of oxidation occurred in tests made in a box at 1 ordinary temperatures, at 158 F, at 212 F., and286? F, and also. tookplace when directly exposed to the sun and a weather. This material also retards oxidation during vulcanization inair.

A pure gum' stock, was make up of 100 parts of spray dried rubber with 10 parts of sulphur, and a similar stock with 5 parts or,

acidcondensatc. Another stock was made up of 100 parts of pale crepe and 10 parts I of sulphur, and a similarone with 5 parts of acid condensate. On aging at158 'F'. after curing the blanks of the spray dried rubber and pale crepe containing no deterioration retarder had almost completely deteriorated atthe 'endot ten days, while the same stockscontaining the acid condensate had deteriorated merely from about .4000 lbs.

7 to somewhat below 3600 lbs. tensile strength, and the acidflcondensate stocks lasted about 2 times as long'bofore completely deteriorating.

l Hot water bottles l'nadej up o'l various stocks both with and without oxidation retarder weretested under the continued action of boiling water, and in each case the bottles made from stock containing the oxidationretarder lastedtrom2 to 2% times as long as those of regular stock before Tests made of other stocks with and without the use of the acid condensate showed great improvement in the acid condensate stocks in tensile strength and permanent set In particular in the case of thread stock aged under constant stretch it was shown that when" aged'in air the acid condensate stock had a i very much less permancnt'set than the blank,

while when'agedin nitrogen theblank and acid condensate stocks had practically the same set, this test proving very conclusively dation'. I

lVlnle the above disclosed examples illustrate'the process as applied to the condensa tron oi acetaldehyde and anil ne 111 acid soluilOIl, I have employed in place of aniline with smaller excellent results mtho-toluidine, par luichne, meta-toluidine, mono-methyl ztIlll.1l1(-,'2111tlnlttktfXyllcllne. v

that the acid condensate actually retards oxi- It will be seen from the above disclosure that the objects oftheinvention previously set :t'orth have been attained, and while spe V cific examples have been given, the invention 2; The process of making a deterioration :retarder for. rubber, which comprises comb ning acetaldehydeand aniline 111. an acid solution having a hydrogen ion concentration greaterthanlXm' I p r 3, The process of making a deterioration phatie aldehyde and an aromatic amine in acid solution. i

The process otlinaking a deterioration retarder for rubber, which comprises combining-equi-molecular portions of acetaldehydeand an aroma ic aminein acid solution.

'SQThe process of making a deterioration rc'tarder tor rubber, which comprises combm mg. equmnolecular portions of acetaldehyde and aniline in acid solution.

my invention, what J 1. claim and. desire to protect byLetters Pat- 1 retarder to-r rubber, which comprises com- 'bming equi-molecular portions of an ali- 6, The process of making adeterioration retarder for rubber, which comprises con inning equmnolecular portions of inietaldehyde and aniline 111 acid solution below 25 C;

' 7. The process of making a deterioration 'retarderi'or rubber, which comprises co1nbining" GqUl-IDOlOCUlfli' portions of acetaldehyde and aniline in hydrochloric acid solu-d ,8. The process ot'making a deteriorationretarder tor rubber, which. comprises combining equi-molecular portions ot acetaldeh de and aliline in hydrochloric acid solu tion below 20 C. f I a 9. The process of making a deterioration retarder for rubber, which comprises dissolving a molecular equivalent of an aromatic amine in acid solution, adding a molecular equivalent of acetaldehyde in solution, precipitating and acetaldehyde aromatic amine condensation product by neutralizing the acid, and separating and washing the precipitate.

10. The process of making a deterioration retarder tor rubber. which comprises dissolving a molecular equivalent of aniline in hydrochloric z i solution. adding a. molecular equivalent of acetaldehyde in solution, precipitating an acetaldehyde-aniline condensation product by the addition of a base, and'separating and washing the precipitate.

11. The process of making a deterioration retarder tor rubber, which comprises dissolving a molecular equivalent of aniline in hydrochloric acid solution, adding a molecular equivalent of acetaldehyde in solution, while stirring, precipitating an acetaldehyde-aniline condensation product by the addition of an equi-niolecular proportion ot. aniline, and separating and washing the precipitate.

12. The process of making a deterioration retarder for rubber, which comprises dissolving a molecular equivalent or aniline in hydrochloric acid solution and cooling, add ing a molecular equivalent of acetaldehyde in solution while stirring and maintaining the temperature below (1, precipitating an acetaldehytie-aniline condensation prod not by the addition, with stirring of an equimolecular proportion of aniline, and separating and washing the precipitate.

13. The process for continuously making a deterioration retarder tor rubber which comprises dissolving aniline in a strong acid solution. reacting upon the aniline with an equi-inolecular proportion of acetaldehyde, precipitating an acetaldehyde-aniline condensation product by the addition of an equi-molecular proportion of aniline, sepa- "ating the precipitate, and again reacting upon the liquid remainder with an equimolecular proportion of acetaldehyde.

14. The process for continuously making a deterioration retarder tor rubber which comprises dissolving aniline in a strong acid solution, reacting upon the aniline with an equi-molecular proportion of acetaldehyde, precipitating an acetaldehyde-aniline condensation product by the addition of an equi-molecular proportion of aniline, separating the precipitate by filtration from the resulting acid solution of aniline, restoring the said solution to its original quantity and acidity, and again reacting upon the solulessees tion with an equi-molecular proportion of acetaldehyde.

15. T he process of making a deterioration retarder tor rubber, which comprises dissolving a molecular equivalent of aniline in a strong acid solution, adding a molecular equivalent of acetaldehyde in solution, precipitating an acetaldehyde-aniline condensation product by substantially neutralizing the acid with sodium l'iydroxiile, and separating and washing the precipitate.

to. The process of making a deterioration retarder for rubber, which comprises dissolving a molecular equivalent of aniline in h -sdrochloric acid. adding a molecular equivalent of acetaloehyde .in solution while maintaining the temperature below 25 (3., neutralizing between .8 and .9 of the acid with sodium hydroxide, thereby precipitating an acetaldehyde-aniline condensation product, and separating and washing the precipitate.

1'7. As a retarder of deterioration of rubber, an acetaldehyde-aromatic amine con deusation product prepared in a strongly acid solution.

18. As a retarder of deterioration of rubber. the acctaldehyde-aniline condensation product formed by the interaction of equimolecular quantities of acetaldehyde and aniline in strongly acid solution.

1.9. As a retarder of deterioration of rubber, the acetaldehyde-aromatic amine condensation product termed by the interaction of equi-molecular quantities of acetaldehyde and an aromatic amine in acid solution.

20. As a retarder 0t deterioration oi rubher, the finely divided solid product of the substantially complete reaction of equimoleeular quantities of aoetaldehyde and aniline in strongly acid solution.

21. As a. retarder of deterioration of rubber, the finely dividd solid product of the substantially complete reaction of equimolecular quantities of acetaldehyde and aniline in a strong acid solution.

22. As a retarder of deterioration of rubber, the solid product of the substantially complete reaction oi equi-molecular quan tities of acetaldehyde and aniline in a strong acid solution, having the form of a yellow powder, and a melting point between 130 C.

Signed at Yew York, county and State of New York, this 19th day of September, 1924.

SIDNEY M. CADVELL. 

